Liquid crystal display device and method for manufacturing the same

ABSTRACT

The present invention provides a liquid crystal display device to be operated at high speed and with high precision by improving performance of a thin-film transistor without increasing cross capacity of gate lines and data lines. On an upper layer of a gate insulator GI at an intersection of gate lines GL and data lines DL to be prepared on an active matrix substrate SUB 1 , which makes up a liquid crystal display panel of a liquid crystal display device, an insulating material with low dielectric constant is dropped by ink jet coating method to prepare another insulator LDP in order to improve performance characteristics of the thin-film transistor to be prepared on a silicon semiconductor layer SI without increasing cross capacity on said intersection.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. application Ser.No. 11/452,978, filed Jun. 15, 2006, the contents of which areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a liquid crystal device of activematrix type and to a method for manufacturing the same. In particular,the invention relates to a thin-film transistor formed on one ofsubstrates of a liquid crystal display panel, which makes up the liquidcrystal display device. The invention also relates to a method formanufacturing the same.

BACKGROUND ART

A liquid crystal display panel to make up a liquid crystal displaydevice of active matrix type has a liquid crystal interposed between asubstrate (an active matrix substrate) and another substrate (a colorfilter substrate). In a manufacturing process to prepare a thin-filmtransistor (TFT) on the active matrix substrate, a plurality of gatelines disposed in parallel to each other and comprising metal film suchas chromium are prepared on said substrate, and a gate electrodeextending from each of said gate lines to each pixel is formed.

FIG. 17 represents diagrams to explain an equivalent circuit of adisplay panel of a liquid crystal display device of active matrix type.FIG. 17 (a) is a circuit diagram of the entire device, and FIG. 17 (b)is an enlarged view of the diagram of a pixel unit PXL in FIG. 17 (a).In FIG. 17 (a), a multiple of pixel units PXL are arranged inmatrix-like form on a display panel PNL. Each pixel PXL is selected at ascan line driving circuit GDR and is turned on according to a displaydata signal from a data line (also called “source line”) driving circuitDDR.

Specifically, in response to the gate line GL selected by the scan linedriving circuit GDR, a display data (voltage) is sent to a thin-filmtransistor TFT on the pixel unit PXL of the display panel PNL via a dataline DL from the data line driving circuit DDR.

As shown in FIG. 17 (b), the thin-film transistor TFT to constitute thepixel unit PXL is provided at an intersection of the gate line GL andthe data line DL. The gate line GL is connected to a gate electrode GTof the thin-film transistor TFT, and the data line DL is connected to adrain electrode or a source electrode (“drain electrode” at this moment)SD2 of the thin-film transistor TFT.

The drain electrode or the source electrode (“source electrode” at thismoment) SD1 of the thin-film transistor TFT is connected to a pixelelectrode PX of a liquid crystal (element) LC. The liquid crystal LC ispositioned between a pixel electrode PX and a common electrode CT and isdriven by a data (voltage) to be supplied to the pixel electrode PX. Anauxiliary capacity Ca to temporarily maintain the data is connectedbetween the drain electrode SD2 and an auxiliary capacity line CL.

FIG. 18 represents a plan view to show a pixel unit PXL of a displaypanel PNL shown in FIG. 17 and a cross-sectional view to explain anarrangement of a thin-film transistor TFT to make up the pixel unit PXL.Specifically, FIG. 18 (a) is a plan view of a pixel unit PXL arranged inmatrix-like form as shown in FIG. 17, and FIG. 18 (b) is across-sectional view of the thin-film transistor TFT in the pixel unitPXL along the line A-A′.

As shown in FIG. 18 (a), in the pixel unit PXL arranged in matrix-likeform, the thin-film transistor TFT is disposed at an intersection of thegate line GL and the data line DL. Also, a pixel electrode PX isconnected to the thin-film transistor TFT, and an auxiliary capacity isformed with the auxiliary capacity line CL.

In FIG. 18 (b), in the thin-film transistor TFT, a gate electrode GT anda gate insulator GI to cover the gate electrode GT are prepared on aninsulating substrate SUB1. On the insulator, a silicon (Si)semiconductor layer SI, an ohmic contact layer (n⁺ Si) NS, a sourceelectrode SD1 and a drain electrode SD2 are sequentially laminated onthe insulator.

To prepare a gate insulator GI, silicon nitride (SiNx) is deposited tocover the gate line GL and the gate electrode GT, and a plurality ofdata lines DL are prepared to intersect the gate lines GL. At the sametime as the preparation of the data lines DL, the source electrode SD1and the drain electrode SD2 are formed on the same layer.

As described above, in a region enclosed by each gate line GL and eachdata line DL, a unit pixel comprising a pixel unit PXL is provided. Thisunit pixel has a sub-pixel of a single color (red, green, or blue) incase of full-color display. Hereinafter, the unit pixel is also simplyreferred as “pixel”. The thin-film transistor (TFT) to make up the pixelunit PXL comprises, as described above, a gate electrode, a siliconsemiconductor film prepared by patterning on the gate electrode, anohmic contact layer (n⁺ silicon) separately formed on upper layer of thesilicon semiconductor film, and a source electrode and a drain electrodeconnected respectively to the separated ohmic contact layer.

On the upper layer of the thin-film transistor, a protective layer PASis deposited. On it, a pixel electrode PX—preferably made of ITO, isprepared by patterning, and it is connected to the source electrode (orto the drain electrode) SD1 via a contact hole provided in theprotective film PAS. An orientation film (not shown) is deposited tocover the pixel electrode PX.

On the other hand, on another substrate (not shown in the figure), acounter electrode (in FIG. 17 (b)) is prepared via a smooth layer(overcoat layer) and a 3-color filter (in case of full-color display).An orientation film is deposited to cover the counter electrode. Anactive matrix substrate (i.e. one of the substrates as described above)is superimposed on it, and a liquid crystal is sealed in a gaptherebetween.

The Patented Reference 1 as given below discloses a method formanufacturing lines of the active matrix substrate as described above bymeans of ink jet coating method. In the Patented Reference 1, the gateelectrode of the thin-film transistor TFT is prepared by ink jet coatingmethod using a liquid containing a conductive material. Also, it isdescribed that a source electrode and a drain electrode of the thin-filmtransistor are prepared by ink jet coating method using a liquidcontaining a semiconductor material.

[Patented Reference 1] JP-2003-318193

The gate insulator to be formed on the active matrix substrate of theliquid crystal display panel is provided to insulate the gate line anddata line. The thinner the gate insulator is, the more the performanceof the thin-film transistor are improved. Also, the thinner the gateinsulator is, the finer the auxiliary capacity line can be produced, andthis contributes to the improvement of aperture rate. However, when thegate insulator is thinner, cross capacity at the intersection with thedata line is increased, and this results in the delay of signal. Also,the counter capacity between the gate line and the counter electrode isalso increased. If the gate insulator is designed thicker to reduce thecross capacity and counter capacity, performance of the thin-filmtransistor are decreased as described above.

It is an object of the present invention to provide a liquid crystaldisplay device, which can be operated at high speed and with highprecision by improving performance characteristics of the thin-filmtransistor without increasing cross capacity and counter capacity.

SUMMARY OF THE INVENTION

To attain the above object, according to the present invention, anotherinsulator is provided by dropping an insulating material with lowdielectric constant by ink jet coating method to an upper layer or to alower layer of the gate insulator at the intersection of the gate lineand the data line, and performance characteristics of the thin-filmtransistor is improved without increasing cross capacity at theintersection and a capacity from the counter electrode (countercapacity).

Also, according to the present invention, an insulating material withlow dielectric constant is dropped by ink jet coating method along thegate line including an intersection with the data line to an upper layeror to a lower layer of a gate insulator to cover the gate line. Thus,the performance characteristics of the thin-film transistor are improvedwithout increasing cross capacity at the intersection and a capacity(counter capacity) with the counter electrode.

After the formation of the data lines, the source electrode, and thedrain electrode, a silicon semiconductor layer is deposited and asemiconductor island is prepared by patterning. Then, the thin-filmtransistor is provided by preparing an ohmic conduct layer, the sourceelectrode, and the drain electrode. After the formation of a protectivefilm, a pixel electrode connected to the source electrode (or drainelectrode) of the thin-film transistor is prepared via a contact holeopened in the protective film. Then, the liquid crystal display panel isprepared by a process already known, and the liquid crystal displaydevice can be provided.

According to the present invention, it is possible to provide coating ofan insulating material with low dielectric constant to the extent asnecessary only on the intersection of the gate line and the data line oron the gate line including the intersection and to an upper layer or toa lower layer of the gate insulator. Thus, without increasing crosscapacity of the intersection and the capacity (counter capacity) withthe counter electrode and without the need to remove unnecessary portionand to perform subsequent process, performance characteristics of thethin-film transistor can be improved. When the insulating material isdropped by ink jet coating, peripheral edge of the insulator can beprepared in a tapered form with gentle slope. Thus, disconnection can beavoided, which may be caused by skipping over as data line goes over thegate line when crossing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents plan views to explain essential processes of a methodfor manufacturing an active matrix substrate of a liquid crystal displaypanel, which constitutes Embodiment 1 of a liquid crystal display deviceaccording to the present invention;

FIG. 2 is a cross-sectional view along the line A-A of the active matrixsubstrate when data lines are prepared in a process (4) as shown in FIG.1;

FIG. 3 represents plan views to explain essential processes of a methodfor manufacturing the active matrix substrate of the liquid crystaldisplay panel, which constitutes Embodiment 2 of the liquid crystaldisplay device of the present invention;

FIG. 4 is a cross-sectional view along the line A-A of the active matrixsubstrate when data lines are prepared in a process (4) as shown in FIG.3;

FIG. 5 represents plan views to explain essential processes of a methodfor manufacturing the active matrix substrate of the liquid crystaldisplay panel, which constitutes Embodiment 3 of the liquid crystaldisplay device of the present invention;

FIG. 6 is a cross-sectional view along the line A-A of the active matrixsubstrate when data lines are prepared in a process (4) as shown in FIG.5;

FIG. 7 represents plan views to explain essential processes of a methodfor manufacturing the active matrix substrate of the liquid crystaldisplay panel, which constitutes Embodiment 4 of the liquid crystaldisplay device of the present invention;

FIG. 8 is a cross-sectional view along the line A-A of the active matrixsubstrate when data lines are prepared in a process (4) as shown in FIG.7;

FIG. 9 represents plan views to explain essential processes of a methodfor manufacturing the active matrix substrate of the liquid crystaldisplay panel, which constitutes Embodiment 5 of the liquid crystaldisplay device of the present invention;

FIG. 10 is a cross-sectional view of the active matrix substrate alongthe line B-B when data lines are prepared in the process (4) of FIG. 9and another substrate is attached to seal the liquid crystal;

FIG. 11 represents plan views to explain essential processes of a methodfor manufacturing the active matrix substrate of the liquid crystaldisplay panel, which constitutes Embodiment 6 of the liquid crystaldisplay device of the present invention;

FIG. 12 is a cross-sectional view of the active matrix substrate alongthe line B-B when data lines are prepared in the process (4) of FIG. 11and another substrate is attached to seal the liquid crystal;

FIG. 13 represents plan views to explain essential processes of a methodfor manufacturing the active matrix substrate of the liquid crystaldisplay panel, which constitutes Embodiment 7 of the liquid crystaldisplay device of the present invention;

FIG. 14 is a cross-sectional view of the active matrix substrate alongthe line B-B when data lines are prepared in the process (4) of FIG. 13and another substrate is attached to seal the liquid crystal;

FIG. 15 represents plan views to explain essential processes of a methodfor manufacturing the active matrix substrate of the liquid crystaldisplay panel, which constitutes Embodiment 8 of the liquid crystaldisplay device of the present invention;

FIG. 16 is a cross-sectional view of the active matrix substrate alongthe line B-B when data lines are prepared in the process (4) of FIG. 15and another substrate is attached to seal the liquid crystal;

FIG. 17 represents an equivalent circuit of a display panel unit of aliquid crystal display device of active matrix type; and

FIG. 18 represents drawings to explain an arrangement of a pixel unitPXL of a display panel PNL shown in FIG. 17 and an arrangement of athin-film transistor TFT to constitute a pixel unit PXL.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Detailed description will be given below on embodiments of the presentinvention referring to the drawings. The structure of the liquid crystaldisplay device of the present invention will be described in connectionwith the manufacturing method as given below.

Embodiment 1

FIG. 1 represents plan views to explain essential processes of a methodfor manufacturing an active matrix substrate of a liquid crystal displaypanel, which constitutes Embodiment 1 of the liquid crystal displaydevice according to the present invention. Here, description will begiven on processes to form data lines and source electrodes and drainelectrodes in the processes (1) to (4). First, (1) Preparation of gateelectrode: a gate line GL is prepared by patterning on surface of aninsulating substrate—preferably a transparent glass substrate. On thegate line GL, a gate electrode GT of a thin-film transistor is providedto protrude on it.

(2) Preparation of island: A gate insulator GI is deposited to cover theentire area of the substrate including the gate line GL and the gateelectrode GT. To form the gate insulator GI, silicon nitride (SiNx) isdeposited by CVD (chemical vapor deposition). Then, an amorphous siliconsemiconductor layer and an n⁺ silicon semiconductor layer (ohmic contactlayer) with silicon mixed with phosphor or the like as impurities areprepared by CVD. By processing the ohmic contact layer, which has beenturned to the amorphous silicon semiconductor layer, a siliconsemiconductor island SI is formed on upper portion of the gate electrodeGT. In this case, the ohmic contact layer to be formed on the upperlayer of the island SI is separately prepared as connecting regions of asource electrode and a drain electrode respectively.

(3) Ink jet coating of the crossing portion: Only on a crossing portionwhere data line crosses the gate insulator GI of the gate line, aninsulating material with low dielectric constant is dropped and coatedby ink jet coating, and another insulator layer LDP is formed. Thisanother insulator LDP will be referred below as the insulator LDP withlow dielectric constant.

(4) Formation of source and channel: On the gate insulator GI, and onthe insulator LDP with low dielectric constant on the gate line GL, asource line, i.e. a data line DL, is formed. In this case, the sourceelectrode SD1 and the drain electrode of the thin-film transistor areprocessed by patterning at the same time, and a channel is providedbetween the source electrode SD1 and the drain electrode. Then, theactive matrix substrate is prepared through a pixel forming process suchas formation of a protective film and formation of a pixel electrode andthrough coating process to form an orientation film.

FIG. 2 is a cross-sectional view of the active matrix substrate alongthe line A-A when the data line is prepared in the process (4) shown inFIG. 1. As shown in the figure, a gate line GL is formed on surface of aglass substrate SUB1. The gate insulator GI is formed over the entiresurface of the glass substrate SUB1 to cover the gate line GL. On thegate line GL on a portion where the gate line GL and the data line crosseach other and on the gate insulator GI, an ink of an insulatingmaterial with low dielectric constant such as an aromatic hydrocarbontype organic polymer and polyallyl ether type organic polymer is droppedby ink jet coating method. When this ink is dried up, it is turned tothe insulator LDP with low dielectric constant.

On the 2-layer insulating structure of the gate insulator GI and theinsulator LDP with low dielectric constant, the data lines DL areprovided to cross. As shown in FIG. 2, peripheral edge of the insulatorLDP with low dielectric constant dropped by ink jet coating method andhardened is turned to a tapered form with gentle slope. As a result, thedata line DL crossing the gate line GL runs over the gate line GL withgentle slope, and this prevents breaking of lines caused by skip-over.Between the data line DL and a counter electrode on a color filtersubstrate (not shown), there is no dielectric substance, which narrowsdown the distance between electrodes except the above-mentioned crossingportion.

According to Embodiment 1, it is possible to improve performancecharacteristics of the thin-film transistor without increasing crosscapacity and counter capacity and to provide a liquid crystal displaydevice to be operated at high speed and with high precision.

Embodiment 2

FIG. 3 represents plan views to explain essential processes of a methodfor manufacturing an active matrix substrate of a liquid crystal displaypanel, which makes up Embodiment 2 of the liquid crystal display deviceaccording to the present invention. Here again, the processes to preparethe data line, the source electrode and drain electrode are described inthe order of (1) to (4). Similarly to Embodiment 1, first, (1)Preparation of gate electrode: A gate line GL is prepared by patterningon the surface of an insulating substrate—preferably a transparent glasssubstrate. On the gate line GL, a gate electrode GT of the thin-filmtransistor is prepared to protrude.

(2) Ink jet coating of the crossing portion: On the gate line GL andonly on the crossing portion where data line intersects, an insulatingmaterial with low dielectric constant is coated by ink jet coating, andan insulator LDP with low dielectric constant is prepared.

(3) Preparation of island: A gate insulator GI is deposited over theentire Substrate including the gate line GL, the gate electrode GT, andthe insulator LDP with low dielectric constant. The gate insulator GI isformed by silicon nitride (SiNx) by CVD. Similarly by CVD processing, anamorphous silicon semiconductor layer and an n⁺ silicon semiconductorlayer (ohmic contact layer) with silicon intermingled with phosphor orthe like as impurities are deposited. By processing the ohmic contactlayer, which has been turned to the amorphous silicon semiconductorlayer, a silicon semiconductor island SI is prepared on upper portion ofthe gate electrode GT. In this case, the ohmic contact layer to beformed on the upper layer of the island SI is separately prepared asconnecting regions of a source electrode and a drain electrode.

(4) Formation of source and channel: On the insulator LDP with lowdielectric constant and on the gate insulator GI, and on the gateinsulator GI on the intersecting gate line GL, a source line, i.e. adata line DL, is prepared. In this case, patterning is performed at thesame time for the source electrode SD1 and the drain electrode of thinfilm transistor, and a channel is formed between the source electrodeSD1 and the drain electrode. Then, through pixel forming process to forma protective film and a pixel electrode and through coating process tocoat an orientation film, an active matrix substrate is prepared.

FIG. 4 is a cross-sectional view of the active matrix substrate alongthe line A-A with the data line prepared in the process (4) of FIG. 3.As shown in the figure, the gate line GL is formed on the surface of aglass substrate SUB1. On the gate line GL and on a portion of the gateline GL where the data line intersects, an ink of an insulating materialwith low dielectric constant such as aromatic hydrocarbon type organicpolymer or polyallyl ether type organic polymer is dropped and coated byink jet coating. When the ink is dried up, it is turned to an insulatorLDP with low dielectric constant. Then, a gate insulator GI is formedover the entire surface of the glass substrate SUB1 to cover the gateline GL, which has the insulator LDP with low dielectric constant at theintersection.

Then, a data line DL is disposed on a 2-layer insulating structure,which comprises the insulator LDP with low dielectric constant and thegate insulator GI. As shown in FIG. 4, peripheral edge of the insulatorLDP with low dielectric constant prepared by ink jet coating andhardened is turned to a tapered form with gentle slope. It forms an edgemore gently tapered than the gate insulator GI on it. As a result, thedata line DL intersecting with the gate line GL goes over the gate lineGL at a gentle angle. Thus, disconnection can be avoided, which may becaused by skip-over when jumping at a steep angle. Between the data lineDL and a counter electrode of a color filter substrate (not shown),there is no dielectric substance, which narrows down the distancebetween electrodes.

According to Embodiment 2, it is possible to improve performancecharacteristics of the thin-film transistor without increasing crosscapacity and counter capacity and to provide a liquid crystal displaydevice to be operated at high speed and with high precision.

Embodiment 3

FIG. 5 represents plan views to explain essential processes of a methodfor manufacturing an active matrix substrate of a liquid crystal displaypanel, which makes up Embodiment 3 of the liquid crystal display deviceaccording to the present invention. In Embodiment 3, the gate line andthe data line are also prepared by ink jet coating. Description will begiven now on the processes to prepare the data line, the sourceelectrode and drain electrode in the order of (1) to (4). First, (1)Preparation of the gate electrode: A gate line and a bank BNK-G to forma groove on the pattern of the gate electrode are provided on thesurface of an insulating substrate—preferably a transparent glasssubstrate. The bank BNK-G and its groove are prepared from aphotosensitive resist by photolithographic method. This is the same inthe other embodiments. An ink containing conductive particles such assilver or copper is dropped into the groove of the bank BNK-G by ink jetcoating and the groove is filled. When the ink is dried up, the gateline GL and the gate electrode GT are prepared by baking.

(2) Preparation of island: A gate insulator GI of SiNx by CVD isdeposited over the entire substrate including the gate line GL, the gateelectrode GT and the bank BNK-G. Then, by similar CVD processing, anamorphous silicon semiconductor layer and an n⁺ silicon semiconductorlayer (ohmic contact layer) with silicon intermingled with phosphor orthe like as impurities are deposited. By processing the ohmic contactlayer, which has been turned to the amorphous silicon semiconductorlayer, a silicon semiconductor island SI is prepared on upper portion ofthe gate electrode GT. In this case, the ohmic contact layer prepared onthe upper layer of the island SI is separately provided as connectingregions of a source electrode and drain electrode respectively.

(3) Ink jet coating of the crossing portion: On the gate insulator GI ofthe gate line and only on the crossing portion where the data linecrosses, an insulating material with low dielectric constant is droppedand coated by ink jet coating, and an insulating layer LDP with lowdielectric constant is prepared.

(4) Formation of source and channel: On the surface of the insulatingsubstrate, a data line, a bank BNK-D to form groove on pattern of thesource electrode and the drain electrode is provided. The bank BNK-D andits groove are prepared from a photosensitive resist byphotolithographic method. This is the same in the other embodiments. Anink containing conductive particles such as silver and copper is droppedinto the groove of the bank BNK-D and the groove is filled. When this isdried up, a data line DL, a source electrode SD1 and a drain electrodeSD2 are prepared by baking. In this case, a channel is formed betweenthe source electrode SD1 and the drain electrode SD2. Then, an activematrix substrate is prepared through pixel forming process such as theformation of a protective film and a pixel electrode and through coatingprocess to coat an orientation film.

FIG. 6 is a cross-sectional view of an active matrix substrate along theline A-A with the data line prepared in the process (4) of FIG. 5. Asshown in the figure, the gate line GL is prepared in the groove of thebank BNK-G formed on the surface of a glass substrate SUB1. A gateinsulator GI is prepared over the entire surface of the glass substrateSUB1 to cover the gate line GL. On the gate insulator GI, an ink of aninsulating material with low dielectric constant such as aromatichydrocarbon type organic polymer or polyallyl ether type organic polymeris dropped by ink jet coating on the gate line GL and on the gate lineGL on a portion where the data line intersects. When this ink is driedup, it is turned to an insulator LDP with low dielectric constant.

On the 2-layer insulating structure of the gate insulator GI and theinsulator LDP with low dielectric constant, the data line DL is preparedto cross it. As shown in FIG. 6, the gate insulator GI is formed flatlyon the bank BNK-G. Peripheral edge of the insulator LD with lowdielectric constant prepared by ink jet coating and hardened is formedin a tapered form with gentle slope. As a result, the data line DL tocross the gate line GL goes over the gate line GL with gentle slope, anddisconnection caused by skip-over when jumping at steep angle can beavoided. Between the data line DL and a counter electrode on a colorfilter substrate (not shown), there is no dielectric substance, whichnarrows down the distance between electrodes except the intersection asdescribed above.

According to Embodiment 3, it is possible to improve performancecharacteristics of the thin-film transistor without increasing crosscapacity and counter capacity and to provide a liquid crystal displaydevice to be operated at high speed and with high precision.

Embodiment 4

FIG. 7 represents plan views to explain essential processes of a methodfor manufacturing an active matrix substrate of a liquid crystal displaypanel, which makes up Embodiment 4 of the liquid crystal display deviceof the present invention. Similarly to Embodiment 3, the gate line anddata line are prepared in Embodiment 4 by ink jet coating method. Hereagain, description will be given on the process to prepare the dataline, the source electrode and the drain electrode in the order of (1)to (4). First, (1) Preparation of gate electrode: On the surface of aninsulating substrate—preferably a transparent glass substrate, a gateline and a bank BNK-G to form a groove on the pattern of the gate lineand gate electrode are provided. An ink containing conductive particlessuch as silver or copper is dropped into the groove of the bank BNK-G tofill it. Then, this is dried up, and a gate line GL and a gate electrodeGT are prepared by baking.

(2) Ink jet coating of the crossing portion: On the gate insulator GI ofthe gate line and only on the crossing portion where the data linecrosses, an insulating material with low dielectric constant is droppedby ink jet process, and an insulator LDP with low dielectric constant isprepared.

(3) Preparation of island: A gate insulator GI is deposited over theentire surface of the substrate including the gate line GL, the gateelectrode GT, and the bank BNK-G. To prepare the gate insulator GI,silicon nitride (SiNx) is deposited by CVD. Then, by similar CVDprocessing, an amorphous silicon semiconductor layer and an n⁺ siliconsemiconductor layer (ohmic contact layer) with silicon intermingled withphosphor or the like as impurities are deposited. By processing theohmic contact layer, which has been turned to the amorphous siliconsemiconductor layer, a silicon semiconductor island SI is prepared onupper portion of the gate electrode GT. In this case, the ohmic contactlayer formed on the upper layer of the island SI is separately providedas connecting regions of a source electrode and a drain electroderespectively.

(4) Formation of source and channel: On the surface of the insulatingsubstrate, a data line and a bank BNK-D with groove formed on thepattern of the source electrode and the drain electrode are disposed. Anink with conductive particles such as silver or copper is dropped intothe groove of the bank BNK-D to fill it. Then, this is dried up, and thedata line DL, a source electrode SD1, and a drain electrode SD2 areprepared. In addition, a channel is formed between the source electrodeSD1 and the drain electrode SD2. Then, the active matrix substrate isprepared through pixel forming process to form a protective film and apixel electrode and through coating process to coat an orientation film.

FIG. 8 is a cross-sectional view of an active matrix substrate along theline A-A with the data line prepared in the process (4) of FIG. 7. Asshown in the figure, a gate line GL is prepared in the groove of thebank BNK-G formed on the surface of the glass substrate SUB1. On thegate line GL on a portion where the gate line GL crosses the data lineand on the gate insulator GI, an ink of an insulating material with lowdielectric constant such as aromatic hydrocarbon type organic polymer,polyallyl ether type organic polymer, etc. is dropped by ink jetcoating. When this ink is dried up, it is turned to an insulator LDPwith low dielectric constant. The gate insulator GI is prepared over theentire surface of the glass substrate SUB1 to cover the insulator LDPwith low dielectric constant.

On the 2-layer insulating structure of the insulator LDP with lowdielectric constant and the gate insulator GI, the data lines DL areformed to cross. As shown in FIG. 8, in the gate insulator GI formed onthe insulator LDP with low dielectric constant, peripheral edge isprepared with gentle slope because of the bank BNK-G. As a result,disconnection can be avoided, which may be caused by skip-over when thedata line DL crossing the gate line GL goes with gentle slope over thegate line GL. Also, between the data line DL and a counter electrode ofa color filter substrate (not shown), there is no dielectric substance,which narrows down distance between electrodes except at theintersection.

According to Embodiment 4, it is possible to improve performancecharacteristics of the thin-film transistor without increasing crosscapacity and counter capacity and to provide a liquid crystal displaydevice to be operated at high speed and with high precision.

Embodiment 5

FIG. 9 represents plan views to explain essential processes of a methodfor manufacturing an active matrix substrate of a liquid crystal displaypanel, which makes up Embodiment 5 of the liquid crystal display deviceof the present invention. Here again, description will be given on theprocesses to prepare the data line, the source electrode, and the drainelectrode in the order of (1) to (4). First, (1) Preparation of gateelectrode: A gate line GL is prepared by patterning on the surface of aninsulating substrate—preferably a transparent glass substrate. On thegate line GL, a gate electrode GT of the thin-film transistor isprepared to protrude.

(2) Preparation of an island: A gate insulator GI is deposited to coverthe entire surface of the substrate including the gate line GL and thegate electrode GT. The insulator GI is prepared by depositing siliconnitride (SiNx) by CVD. Then, an amorphous silicon semiconductor layerand an n⁺ silicon semiconductor layer (ohmic contact layer) with siliconintermingled with phosphor or the like as impurities are deposited bysimilar CVD processing. By processing the ohmic contact layer, which hasbeen turned to the amorphous silicon semiconductor layer, a siliconsemiconductor island SI is prepared on upper portion of the gateelectrode GT. In this case, the ohmic contact layer formed on the upperlayer of the island SI is separately provided as connecting regions ofthe source electrode and the drain electrode respectively.

(3) Ink jet coating of gate line: On the gate insulator GI of the gateline and not only on the crossing portion where data line crosses butalso along the gate line GL, an ink of an insulating material with lowdielectric constant is dropped by ink jet process, and an insulator LDPwith low dielectric constant is formed. The insulator LDP with lowdielectric constant is prepared on upper layers of all of the gate linesGL at least within a display region (a region where a multiple of pixelsare arranged in matrix-like form) of the active matrix substrate.

(4) Formation of source and channel: On the gate insulator GI and on theinsulator LDP with low dielectric constant on the crossing gate line GL,a source line, i.e. a data line DL, is prepared. In this case, thesource electrode SD1 of the thin-film transistor and the drain electrodeare prepared at the same time by patterning, and a channel is formedbetween the source electrode SD1 and the drain electrode. Then, anactive matrix substrate is prepared through pixel forming process toform a protective film and a pixel electrode, and through coatingprocess to coat an orientation film.

FIG. 10 is a cross-sectional view of an active matrix substrate alongthe line B-B with the data line prepared in the process (4) of FIG. 9,and a liquid crystal is sealed by attaching another substrate on it. Asshown in the figure, a gate line GL is prepared on the surface of theglass substrate SUB1, which makes up the active matrix substrate. Thegate insulator GI is formed on the entire surface of the glass substrateSUB1 to cover the gate line GL. On the gate line GL and on the gate lineGL of a portion where data line crosses and on the gate insulator GI, anink of an insulating material with low dielectric constant such asaromatic hydrocarbon type organic polymer, polyallyl ether type organicpolymer, etc. is dropped by ink jet coating. When this ink is dried up,it is turned to an insulator LDP with low dielectric constant on theinsulator GI along the gate line GL.

On the 2-layer insulating structure of the gate insulator GI and theinsulator LDP with low dielectric constant, the data line DL is preparedto cross. As shown in FIG. 10, peripheral edge of the insulator LDF withlow dielectric constant is formed in a tapered form with gentle slope.As a result, disconnection can be avoided, which may be caused byskip-over when the data line DL crossing the gate line GL goes over thegate line GL at a steep angle. Also, between the data line DL and acounter electrode CT of the color filter substrate SUB2, there is nodielectric substance, which narrows down the distance between electrodesexcept the portion of the gate line GL including the intersection asdescribed above. A liquid crystal LC is sealed between an orientationfilm ORI1 on the active matrix substrate SUB1 and an orientation filmORI2 on the color filter substrate SUB2.

According to Embodiment 5, cross capacity and counter capacity are notincreased. Between the signal lines such as data line and the counterelectrode, there is only an insulator LDP with low dielectric constanton the gate line GL as a dielectric substance to narrow down thedistance between electrodes, and it is not a structure to extensivelyincrease the capacity. For this reason, it is possible to provide aliquid crystal display device to be operated at high speed and with highprecision without decreasing the performance characteristics of thethin-film transistor.

Embodiment 6

FIG. 11 represents plan views to explain essential processes of a methodfor manufacturing an active matrix substrate of a liquid crystal displaypanel, which makes up Embodiment 6 of the liquid crystal display deviceof the present invention. Here again, description will be given on theprocesses to prepare the data line, the source electrode, and the drainelectrode in the order of (1) to (4). First, (1) Preparation of gateelectrode: A gate line GL is prepared by patterning on the surface of aninsulating substrate—preferably a transparent glass substrate. On thegate line GL, a gate electrode GT of the thin-film transistor is formedto protrude.

(2) Ink jet coating of the gate line: On the gate line, not only on thecrossing portion where data line crosses but also along the gate lineGL, an insulating material with low dielectric constant is dropped andcoated, and an insulator LDP with low dielectric constant is prepared.The insulator LDP with low dielectric constant is prepared on upperlayers of all gate lines GL at least within a display region (a regionwhere a multiple of pixels are arranged in matrix-like form) of theactive matrix substrate.

(3) Preparation of island: A gate insulator GI is deposited on the gateline GL, the gate electrode GT, and over the entire surface of thesubstrate including the insulator LDP with low dielectric constant. Toprepare the gate insulator GI, silicon nitride (SiNx) is deposited byCVD. Then, by similar CVD processing, an amorphous silicon semiconductorlayer and an n⁺ silicon semiconductor layer (ohmic contact layer) withsilicon intermingled with phosphor or the like as impurities aredeposited. By processing the ohmic contact layer, which has been turnedto the amorphous silicon semiconductor layer, a silicon semiconductorisland SI is prepared on upper portion of the gate electrode GT. In thiscase, the ohmic contact layer prepared on the upper layer of the islandSI is separately provided as connecting regions of the source electrodeand the drain electrode respectively.

(4) Formation of source and channel: On the gate insulator GI and on theinsulator LDP with low dielectric constant on the intersecting gate lineGL, a source line, i.e. a data line DL, is prepared. In this case,patterning is performed at the same time on the source electrode SD1 andthe drain electrode of the thin-film transistor, and a channel is formedbetween the source electrode SD1 and the drain electrode. Then, anactive matrix substrate is prepared through pixel forming process toform a protective film and a pixel electrode and through coating processto coat an orientation film.

FIG. 12 is a cross-sectional view of an active matrix substrate alongthe line B-B with the data line prepared in the process (4) of FIG. 11,and a liquid crystal is sealed by attaching another substrate. As shownin the figure, the gate line GL is prepared on the surface of the glasssubstrate SUB1, which makes up the active matrix substrate. An insulatorLDP with low dielectric constant is prepared on the gate line GLincluding a portion where data line crosses and a gate insulator GI isprepared on it. To prepare the insulator LDP with low dielectricconstant, an ink of an insulating material with low dielectric constantsuch as aromatic hydrocarbon type organic polymer, polyallyl ether typeorganic polymer, etc. is dropped by ink jet coating method. When it isdried up, it is turned to an insulator LDP with low dielectric constanton the gate insulator GI along the gate line GL.

On the 2-layer insulating structure of the insulator LDP with lowdielectric constant and the gate insulator GI, the data line DL isprepared to cross. As shown in FIG. 12, when ink is dropped by ink jetcoating method and is hardened, peripheral edge of the insulator LDPwith low dielectric constant is prepared in a tapered form with gentleslope. As a result, the data line DL crossing the gate line GL goes overthe gate line GL at gentle slope, and disconnection can be avoided,which may be caused by skip-over when jumping at a steep angle. Also,between the data line DL and the counter electrode CT of the colorfilter substrate SUB2, there is no dielectric substance, which narrowsdown the distance between electrodes except a portion of the gate lineGL including the intersection as described above. A liquid crystal LC issealed between an orientation film ORI1 on the active matrix substrateSUB1 and an orientation film ORI2 on the color filter substrate SUB2.

According to Embodiment 6, cross capacity and counter capacity are notincreased. Between the signal lines such as data line and the counterelectrode, there is only an insulator LDP with low dielectric constanton the gate line as a dielectric substance to narrow down the distancebetween electrodes, and it is not a structure to extensively increasethe capacity. For this reason, it is possible to provide a liquidcrystal display device to be operated at high speed and with highprecision without decreasing the performance characteristics of thethin-film transistor.

Embodiment 7

FIG. 13 represents plan views to explain essential processes of a methodfor manufacturing an active matrix substrate of a liquid crystal displaypanel, which makes up Embodiment 7 of the liquid crystal display deviceof the present invention. Here again, description will be given on theprocesses to prepare the data line, the source electrode and the drainelectrode in the order of (1) to (4). First, (1) Preparation of gateelectrode: A gate line and a bank BNK-G with groove pattern of the gateelectrode are prepared on the surface of the insulatingsubstrate—preferably a transparent glass substrate. An ink containingconductive particles such as silver or copper is dropped into thegrooves of the bank BNK-G by ink jet coating method. It is then driedup, and a gate line GL and a gate electrode GT are prepared by baking.

(2) Preparation of island: A gate insulator GI is deposited over theentire surface of the substrate including the gate line GL, the gateelectrode GT and the bank BNK-G. To prepare the gate insulator GI,silicon nitride (SiNx) is deposited by CVD. Then, by similar CVDprocessing, an amorphous silicon semiconductor layer and an n⁺ siliconsemiconductor layer (ohmic contact layer) with silicon intermingled withphosphor or the like as impurities are deposited. By processing theohmic contact layer, which has been turned to the amorphous siliconsemiconductor layer, a semiconductor island SI is prepared on upperportion of the gate electrode GT. In this case, the ohmic contact layerprepared on the upper layer of the island SI is provided separately asconnecting regions of the source electrode and the drain electroderespectively.

(3) Ink jet coating of the gate line: On the gate insulator GI of thegate line, and not only on the crossing portion where data line crossesbut also along the gate line GL, an ink of an insulating material withlow dielectric constant is dropped by ink jet coating method, and aninsulator LDP with low dielectric constant is prepared. The insulatorLDP with low dielectric constant is formed on upper layers of all gatelines GL at least within a display region (a region where a multiple ofpixels are arranged in matrix-like form) of the active matrix substrate.

(4) Formation of source and channel: On the gate insulator GI, and onthe insulator LDP with low dielectric constant on the crossing gate lineGL, the data line, and the bank BNK-D with groove pattern of the sourceelectrode SD1 and the drain electrode SD2 are prepared. An inkcontaining conductive particles such as silver or copper is dropped intothe groove of the bank BNK-G. Then, it is dried up, and the source line,i.e. the data line DL, and the source electrode SD1 and the drainelectrode SD2 are prepared by baking. In this case, a channel is formedbetween the source electrode SD1 and the drain electrode. Then, anactive matrix substrate is prepared through pixel forming process toform a protective film, a pixel electrode, etc. and through coatingprocess to coat the orientation film.

FIG. 14 is a cross-sectional view of an active-matrix substrate alongthe line B-B with data line prepared in the process (4) of FIG. 13, andthe liquid crystal is sealed by attaching another substrate. As shown inthe figure, a gate line GL is prepared on the entire surface of theglass substrate SUB1, which constitutes the active matrix substrate. Agate insulator GI is prepared over the entire surface of the glasssubstrate SUB1 to cover the gate line GL. The gate insulator GI isprepared in flat form because of the presence of the bank BNK-G. On thegate line where the gate line GL and the data line intersect, and on thegate insulator GI, an ink of an insulating material with low dielectricconstant such as aromatic hydrocarbon type organic polymer, polyallylether type organic polymer, etc. is dropped by ink jet coating. When theink is dried up, it is turned to an insulator LDP with low dielectricconstant on the gate insulator GI along the gate line GL.

On the 2-layer insulating structure comprising the gate insulator GI andthe insulator LDP with low dielectric constant, a data line DL isprepared to cross. As shown in FIG. 14, when ink is dropped by ink jetcoating method and is hardened, peripheral edge of the insulator LD withlow dielectric constant is formed in a tapered form with gentle slope.As a result, the data line DL crossing the gate line GL goes over thegate line GL with gentle slope, and disconnection can be avoided, whichmay be caused by skip-over when jumping at a steep angle. Also, betweenthe data line DL and the counter electrode CT of the color filtersubstrate SUB2, there is no dielectric substance, which narrows down thedistance between electrodes except a portion of the gate line GLincluding the intersection as described above. A liquid crystal LC issealed between an orientation film ORI1 on the active matrix substrateSUB1 and an orientation film ORI2 on the color filter substrate SUB2.

According to Embodiment 7, cross capacity and counter capacity are notincreased. Between the signal lines such as data line and the counterelectrode, there is only an insulator LDP with low dielectric constanton the gate line as a dielectric substance to narrow down the distancebetween electrodes, and it is not a structure to extensively increasethe capacity. For this reason, it is possible to provide a liquidcrystal display device to be operated at high speed and with highprecision without decreasing the performance characteristics of thethin-film transistor.

Embodiment 8

FIG. 15 represents plan views to explain essential processes of a methodfor manufacturing an active matrix substrate of a liquid crystal displaypanel, which makes up Embodiment 8 of the liquid crystal display deviceof the present invention. Here again, description will be given on theprocesses to prepare the data line, the source electrode and the drainelectrode in the order of (1) to (4). First, (1) Preparation of gateelectrode: A gate line and a bank BNK-G with groove pattern of the gateelectrode are prepared on the surface of the insulatingsubstrate—preferably a transparent glass substrate. An ink containingconductive particles such as silver or copper is dropped into thegrooves of the bank BNK-G by ink jet coating method. It is then driedup, and a gate line GL and a gate electrode GT are prepared by baking.

(2) Ink jet coating of the gate line: On the gate insulator GI of thegate line, and not only on the crossing portion where data line crossesbut also along the gate line GL, an ink of an insulating material withlow dielectric constant is dropped by ink jet coating method, and aninsulator LDP with low dielectric constant is prepared. The insulatorLDP with low dielectric constant is formed on upper layers of all gatelines GL at least within a display region (a region where a multiple ofpixels are arranged in matrix-like form) of the active matrix substrate.

(3) Preparation of island: A gate insulator GI is deposited over theentire surface of the substrate including the gate line GL, the gateelectrode GT and the bank BNK-G. To prepare the gate insulator GI,silicon nitride (SiNx) is deposited by CVD. Then, by similar CVDprocessing, an amorphous silicon semiconductor layer and an n⁺ siliconsemiconductor layer (ohmic contact layer) with silicon intermingled withphosphor or the like as impurities are deposited. By processing theohmic contact layer, which has been turned to the amorphous siliconsemiconductor layer, a semiconductor island SI is prepared on upperportion of the gate electrode GT. In this case, the ohmic contact layerprepared on the upper layer of the island SI is provided separately asconnecting regions of the source electrode and the drain electroderespectively.

(4) Formation of source and channel: On the gate insulator GI, and onthe insulator LDP with low dielectric constant on the crossing gate lineGL, the data line, and the bank BNK-D with groove pattern of the sourceelectrode SD1 and the drain electrode SD2 are prepared. An inkcontaining conductive particles such as silver or copper is dropped intothe groove of the bank BNK-G. Then, it is dried up, and the source line,i.e. the data line DL, and the source electrode SD1 and the drainelectrode SD2 are prepared by baking. In this case, a channel is formedbetween the source electrode SD1 and the drain electrode. Then, anactive matrix substrate is prepared through pixel forming process toform a protective film, a pixel electrode, etc. and through coatingprocess to coat the orientation film.

FIG. 16 is a cross-sectional view of an active matrix substrate alongthe line B-B with data line prepared in the process (4) of FIG. 15 withthe liquid crystal sealed by attaching another substrate. As shown inthe figure, a gate line GL is prepared on the surface of the glasssubstrate SUB1, which makes up the active matrix substrate. Including aportion where the gate line GL and the data line DL intersect, an ink ofan insulating material with low dielectric constant such as aromatichydrocarbon type organic polymer, polyallyl ether type organic polymer,etc. is dropped by ink jet coating method. When the ink is dried up, itis turned to an insulator LDP with low dielectric constant on the gateinsulator GI along the gate line GL. A gate insulator GI is prepared onit. The gate insulator GI is prepared in flat form because of thepresence of the bank BNK-G.

On the 2-layer insulating structure comprising the insulator LDP withlow dielectric constant and the gate insulator GI, the data line DL isprepared to cross. As shown in FIG. 16, when ink is dropped by ink jetcoating method and is hardened, peripheral edge of the insulator LDPwith low dielectric constant is formed in a tapered form with gentleslope. As a result, the data line intersecting the gate line GL goesover the gate line GL at a gentle angle, and disconnection can beavoided, which may be caused by skip-over when jumping at a steep angle.Also, between the data line DL and the counter electrode CT of the colorfilter substrate SUB2, there is no dielectric substance, which narrowsdown the distance between electrodes except a portion of the gate lineGL including intersection as described above. A liquid crystal LC issealed between an orientation film ORI1 on the active matrix substrateSUB1 and an orientation film ORI2 on the color filter substrate SUB2.

According to Embodiment 8, cross capacity and counter capacity are notincreased. Between the signal lines such as data line and the counterelectrode, there is only an insulator LDP with low dielectric constanton the gate line as a dielectric substance to narrow down the distancebetween electrodes, and it is not a structure to extensively increasethe capacity. For this reason, it is possible to provide a liquidcrystal display device to be operated at high speed and with highprecision without decreasing the performance characteristics of thethin-film transistor.

Here, description will be given on concrete effects of the presentinvention on capacity at the intersection in Embodiment 3 and on thecounter electrode in Embodiment 7.

Now, description will be given on capacity at the intersection asdescribed in connection with Embodiment 3 by referring to thecross-sectional structure of FIG. 6. Capacity C₀ of the intersection ofonly the gate insulator GI is given by:C ₀=(∈_(gi) /d _(gi))S=(7.0/0.4)Swhere

d_(gi): Thickness of gate insulator GI (0.4 μm)

∈_(gi): Dielectric constant of gate insulator GI (7.0)

S: Area of intersection

when a gate insulator GI is present between the gate line GL and thedata line DL at the intersection of both lines.

Here, it is assumed that the thickness of the insulator LDP with lowdielectric constant coated on the gate insulator GI by ink jet coatingmethod is d. Then, the capacity C of the intersection is given by:C=C ₀{1/(1+d∈ _(gi) /d _(gi)∈)}where

-   -   d: Thickness of the insulator LDP with low dielectric constant    -   ∈: Dielectric constant of the insulator LDP with low dielectric        constant

Here, if it is supposed that the dielectric constant ∈ of the insulatorLDP with low dielectric constant is approximately 3, and when thethickness d of the insulator LDP with low dielectric constant ischanged, the capacity C at the intersection is given as:d=0.4 μm→C=0.30C₀d=0.8 μm→C=0.18C₀d=1.2 μm→C=0.13C₀

Now, the counter capacity as explained in connection with Embodiment 7is now described by referring to the cross-sectional structure shown inFIG. 14. The capacity C₀ of the intersection of the gate insulator GIonly is given by:C ₀={(∈_(gi)·∈_(lc)/(d _(gi)∈_(lc) +d _(lc)∈_(gi))}Swhere

-   -   d_(gi): Thickness of gate insulator GI (0.4 μm)    -   ∈_(gi): Dielectric constant of gate insulator GI(7.0)    -   d_(lc): Thickness of liquid crystal LC(3.5 μm)    -   ∈_(lc): Dielectric constant of liquid crystal LC(8.5)    -   S: Area of opposing portion of the gate line GL and the counter        electrode CT

When the insulator LDP with low dielectric constant is prepared by inkjet coating along the gate insulator GI, the counter capacity C is givenby:C=C ₀[1/{(1+(d∈ _(gi)∈_(lc))/(d _(gi)∈_(lc) +d _(lc)∈_(gi))∈]where

-   -   d: Thickness of the insulator LDP with low dielectric constant    -   ∈: Dielectric constant of the insulator LDP with low dielectric        constant

Here, if it is assumed that dielectric constant ∈ of the insulator LDPwith low dielectric constant is approximately 3, and when the thicknessd of the insulator LDP with low dielectric constant is changed, thecapacity C of the intersection is given by:d=1 μm→C=0.58C₀d=2 μm→C=0.41C₀d=3 μm'C=0.32C₀

The embodiments as described above can be combined as appropriate, andit is needless to say that various changes and modifications of thepresent invention can be made without departing from the spirit and thescope of the present invention.

1. A liquid crystal display device with a liquid crystal interposedbetween a first insulating substrate and a second insulating substrate,wherein said liquid crystal display device comprises: a plurality ofgate lines prepared in parallel to each other and disposed on said firstinsulating substrate; a plurality of data lines prepared in parallel toeach other and being disposed to intersect via said gate line insulatinglayer; each of regions enclosed by said gate lines and said data linesis regarded as a unit pixel region, and a region where said plurality ofgate lines and said plurality of data lines cross each other makes up adisplay region; said liquid crystal display device further comprising athin-film transistor, consisting of a gate electrode extending from saidgate line to said unit pixel region, a gate insulator to cover said gateline and said gate electrode, a semiconductor layer sequentiallyprepared on said gate insulator, an ohmic contact layer separatelyprepared on surface of said semiconductor layer, and a source electrodeand a drain electrode formed on said separated ohmic contact layer; andsaid insulating layer at the intersection of said gate line and saiddata line has a 2-layer structure, comprising said gate insulator and aninsulator with low dielectric constant prepared by ink jet coating on anupper layer or on a lower layer of said gate insulator.
 2. A liquidcrystal display device with a liquid crystal interposed between a firstinsulating substrate and a second insulating substrate, wherein saidliquid crystal display device comprises: a plurality of gate linesprepared in parallel to each other and disposed on said first insulatingsubstrate; a plurality of data lines prepared in parallel to each otherand being disposed to intersect via said gate line insulating layer;each of regions enclosed by said gate lines and said data lines isregarded as a unit pixel region, and a region where said plurality ofgate lines and said plurality of data lines cross each other makes up adisplay region; said liquid crystal display device further comprising athin-film transistor, consisting of a gate electrode extending from saidgate line to said unit pixel region, a gate insulator to cover said gateline and said gate electrode, a semiconductor layer sequentiallyprepared on said gate insulator, an ohmic contact layer separatelyprepared on surface of said semiconductor layer, and a source electrodeand a drain electrode formed on said separated ohmic contact layer; andover the entire area of said display region, said gate insulating layeron said gate line has a 2-layer structure, comprising said gateinsulator and an insulator with low dielectric constant prepared by inkjet coating along said gate line on an upper layer or on a lower layerof said gate insulator.
 3. A liquid crystal display device according toclaim 1 or 2, wherein said insulator with low dielectric constant is aheat-resistant resin.
 4. A liquid crystal display device according toclaim 1 or 2, wherein said insulator with low dielectric constant isaromatic hydrocarbon type organic polymer or a polyallyl ether typeorganic polymer.